This work will facilitate more effective drug abuse prevention and treatment efforts on a societal level by enhancing the accuracy of drug abuse measurement. Specifically, this study will provide definitive answers regarding the viability of incorporating biological measurement of drug use in the context of general population household surveys on drug abuse. The proposed study will evaluate the feasibility and utility of three different types of biological measurement procedures (hair, saliva, and urine testing) to be used as an adjunct to a household survey on drug abuse. This study will compare the relative acceptability of the different biological test methods among survey participants through household surveys of 600 randomly selected subjects residing in the City of Chicago. By randomly assigning subjects to either a high or low incentive drug test condition, this study will evaluate the role of alternative incentive strategies on participation in biological measurement. Through quantitative and qualitative analyses, this study will assess the myriad of subject, interview condition, and procedural variables associated with drug test participation in household surveys. This study will examine impact of prior exposure to drug testing and perceptions about drug testing accuracy on willingness to participate in biological measurement. The study will also gain an understanding of adult willingness to provide consent for similar drug testing in children. Alternative statistical procedures for constructing prevalence estimators from multiple biological measures will be explored. Results derived from biological assessments will be compared with responses to questions about drug use provided in an Audio Computer Assisted Self Interview that precedes the biological assessment. Taking into account factors influencing drug test participation, these comparisons will be used to evaluate the extent of underreporting of drug use in the general population. Subject and drug use variables associated with drug use underreporting will be fully analyzed. The utility of hair testing will be further evaluated by examining whether a new confirmation process (negative ion screening) yields increased sensitivity for detecting marijuana metabolites.